GB2397094A - Over-centre toggle latch - Google Patents

Abstract

An over-centre toggle latch mainly intended for securing together two structural parts, comprises a keeper 1 for attachment to one structural part, a base 2 for attachment to a second structural part, a lever arm 3 pivoted to the base 2, a latch arm 4 with a hooked one end 4a to engage over a lip 1b of the keeper 1 with the other end 4b of the latch arm 4 being snap-coupled through a pivot 3a to the lever arm 3. The lever arm 3 has spaced side members 3b and 3c connected together by a first transverse web forming the pivot 3a for the other end 4b of the latch arm 4 and a second transverse web 3d forming a second pivotal connection with the base 2. The base 2 has an inverted U-shaped saddle part 2a which seats over and embraces the second transverse web 3d. A retainer 2b seats in the saddle 2a to secure the second web 3d therein in a pivotal manner. The side members 3b and 3c, in combination with the base 2, may include co-operating projections 2c and detents 3e whereby the lever may be moved into one of a plurality of angular positions.

Description

Title: Over-centre latch.

This invention relates to an over-centre latch. Such latches are used for a variety of purposes such as securing lids and closures of cases and containers, retaining panels and other component parts particularly such parts used on vehicles Latches of the kind to which this invention relates compose a base for attachment to one part, usually a fixed structure, a keeper for attachment to a second part, usually a removable structure, a latch arm with a hooked end to engage a lip of the keeper, the latch arm being coupled to a lever pivoted to the base. The construction is such that as the lever is pressed towards the base the arm is pulled downwards and inwards to apply a force to the keeper. In the terminal position the lever passes an over-centre point and locks against the base. The operation is due to the relative positioning of the lever pivot point on the base and the pivot point of the arm on the lever.

Known latches for heavy-duty commercial use are made of metal and a disadvantage Is that the parts are subject to wear resulting in the arm losing tension force and thus becoming loose on the keeper. The result is that the lever is then not subject to pressure and the over-centre locking tension is lost no which can result In release of the arm through vibration or accidental contact.

It is an object of this invention to provide an over-centre latch which may substantially avoid the aforesaid problem According to this invention there is provided an over-centre latch for securing together two structural parts, the latch comprising a keeper for attachment to one structural part, a base for attachment to a second structural part, a lever arm pivoted to the base, a latch arm with a hooked one end to engage over a lip of the keeper with the other end of the latch arm being coupled through a pivot to the lever arm, the lever arm having spaced side members connected by a first transverse web forming a first pivotal connection with the other end of the latch arm and a second transverse web forming a second pivotal connection with the base.

The over-centre action of the latch is achieved, as is known, through the relative alignment of the lip on the keeper and the first and second pivots. The keeper lip has a defined fixed position relative to the second pivotal connection whereas the first pivotal connection moves around the second pivotal connection and passes from a latch open position, through an aligned position, to a terminal latched over-centre position in which the lever arm abuts the base.

The latch arm may have an arch shape with each end terminating in a retroverted portion to engage, respectively, the keeper lip and the latch arm pivot point. This arch shape provides a degree of flexure under load to accommodate the over-centre movement whilst still providing a retention force preventing the lever arm returning to the unlatched position.

The keeper may be associated with, or integral with, the relevant part of the structure and thus not a discrete part of the latch defined by this invention.

so The transverse webs may comprise cylindrical parts integral with the side members The other end of the latch arm is formed with a retroverted portion adapted to snap-engage the first web The base may have an inverted U shaped saddle part which embraces the second transverse web A retainer may seat in the saddle to secure the second web therein in a pivotal manner One or both side members of the lever arm may, in combination with the base, include co-operatng projections and detents whereby the lever may be moved into one of a plurality of angular positions The positions may correspond to. the lever arm open enabling the latch arm to be engaged or disengaged with the keeper, The lever arm In a position where the latch arm is engaged with the keeper but not tensioned; the lever arm In a position where the latch arm is tensioned and secured. The detents assist in the latch remaining closed to prevent accidental opening particularly due to vibration.

The second transverse web of the lever arm forming the second pivotal connection with the base may have a planar portion adjacent a lower side of the latch arm, initial rotation of the lever arm about the axis of the second pivotal connection initially producing contact between an edge of the planar portion and the lower side of the latch arm and imparting a lifting force to the latch arm.

In a closed position, the latch arm partially locates, at the other end, within the spaced side members of the lever arm to produce a flush surface.

The other end of the latch arm can have a reduced width where it lies between the side members with the one end of the latch arm having a width coextensive with the side surfaces of the spaced side members of the lever arm This produces a construction with flush sides without projecting parts and so a smooth top surface when closed.

The latch is preferably made from a plastics material conveniently by mouldng of the parts.

One embodiment according to this invention as an example only is described In conjunction with the drawings. In the drawings: Fig 1 shows a plan view of an over-centre latch according to this invention # Fig. 2 shows a longitudinal cross-section on A - A of Fig. 1, Fig 3 shows the component parts of the latch of figs. 1 and 2 separated, Fig. 4a and 4b show the latch in an open position from opposed sides but without the keeper, Fig. 5a and 5b show the latch as in Fig. 4 engaged but not closed, and Fig. 6a and 6b show the latch as in Fig. 4 but here fully closed.

Referring to the drawings the over-centre latch according to this invention Is mainly intended for securing together two structural parts (not shown) such as containers or panels of vehicles. The latch shown comprises a keeper 1 for attachment to one structural part by screws or bolts passing through the apertures 1 a, a base 2 for attachment through apertures 2f to a second structural part, a lever arm 3 pivoted to the base 2, a latch arm 4 with a hooked one end 4a to engage over a lip 1 b of the keeper 1 with the other end 4b of the latch arm 4 being coupled through a pivot 3a to the lever arm 3. The latch arm 4 has a slightly concave curved inner surface and a convex outer surface. This permits slight flexure resulting in longitudinal extension to permit opening action. This construction also exerts a retaining tension along the arm 4 when the latch is closed.

The lever arm 3 has spaced planar side members 3b and 3c connected together by a first transverse web forming the pivot 3a for the other end 4b of the latch arm 4 and a second transverse web 3d forming a second pivotal connection with the base 2 The transverse webs 3a and 3d comprise cylindrical pins integral with the side members 3b and 3c. The other end of the latch arm 4 is formed with a retroverted portion 4c adapted to snap-engage the first web 3a The base 2 has an inverted U-shaped saddle part 2a which seats over and embraces the second transverse web 3d. A retainer 2b may seat In the saddle 2a to secure the second web 3d therein in a pivotal manner One or both side members 3b and 3c, in combination with the base 2, may include co-operatng projections 2c (see side of part 2b in Fig. 3) and detents Be whereby the lever may be moved into one of a plurality of angular positions. The positions may correspond to: Fig 4 the lever arm open enabling the latch arm to be engaged or disengaged with the keeper; Fig. 5 - the lever arm in a position where the latch arm is engaged with the keeper but not tensioned; Fig. 6 - the lever arm in a position where the latch arm is tensioned and secured. The keepems not shown in Figs. 4, 5 and 6. The projections and detents 2c and 3e assist in the latch remaining in a selected position and when the latch is closed prevent vibration loosening the connection.

The transverse web 3d has a flat upper surface 3f which accommodates the rib 4d on the under side of latch arm 4. Thus as the lever arm is raised from the position shown In Fig. 2 the edge of the flat presses against the rib to assist the Initial opening action. This avoids loading the pivot 3a excessively.

This arrangement also provides a stop when arm 3 is in the fully latched position.

The component parts of the latch are preferably made from a plastics material conveniently by moulding of the parts.

A ring pull locking pin 5 may be Included with a spigot 5a which may be Inserted into the aperture 3g of the lever arm 3 to engage a hoop 2e in the base 2. This locks the lever arm 3 to the base 2 when the latch Is closed.

The construction has several advantageous features The pivotal connections have their loads spread over a greater pivot area thus avoiding wear at the pivots which is a problem with metal catches resulting in looseness over time. The plastics material Is not subject to permanent deformation through fatigue or significant wear thus giving a longer service life. The plastics material provides a longer lasting shake-proof latch through the slight elastic flexure when the latch is closed. The latch is designed not to corrode and thus has a long service life. The lever arm has positive click-stop positions to hold the arm at the selected angle when open, engaged or fully latched. This being effected by the projections 2c and detents 3e.

It will be seen that the component parts connect without using extraneous pins or rivets and in particular the lever arm locates over the base and is held by the Insert with the latch arm snap-engaging the pivot through the formation of the retroverted end.

Claims (1)

1. CLAIMS: 1. An over-centre latch for securing together two structural

   parts, the latch comprising, a) a keeper for attachment to one structural part, b) a base for attachment to a second structural part; c) a lever arm pivoted to the base; d) a latch arm with a hooked one end to engage over a lip of the keeper with the other end of the latch arm being coupled through a pivot to the lever arm, the lever arm having spaced side members connected by a first transverse web forming a first pivotal connection with the other end of the latch arm and a second transverse web forming a second pivotal connection with the base.

   2. An over-centre latch in accordance with claim 1, wherein the overcentre action of the latch Is achieved through the relative alignment of the lip on the keeper and the first and second pivotal connections, the keeper lip having a defined fixed position relative to the second pivotal connection, the lever arm producing movement of the first pivotal connection around the second pivotal connection and passing from a latch open position, through an aligned position, to a terminal latched and over-centre position in which the lever arm abuts the base.

   3 An over-centre latch In accordance with claim 1 or 2, wherein the transverse webs have at least part cylindrical profiles and are integral with the side members.

   4. An over-centre latch in accordance with claim 1, 2 or 3, wherein the other end of the latch arm is formed with a retroverted portion defining a channel adapted to snap-engage with the first web to form the first pivotal connection.

   An over-centre latch in accordance with any preceding claim, wherein the base has an inverted U-shaped saddle part defining a channel which embraces the second transverse web to form the second pivotal connection.

   o 6 An over-centre latch in accordance with claim 5, wherein a retainer seats in the saddle to secure the second web therein in a pivotal manner.

   7. An over-centre latch in accordance with any preceding claim, wherein one or both side plates, in combination with the base, include cooperating projections and detents whereby the lever may be moved into one of a plurality of angular positions.

   8. An over-centre latch in accordance with claim 7, wherein the positions include; a) the lever arm open enabling the latch arm to be engaged or disengaged with the keeper; b) the lever arm in a position where the latch arm Is engaged with the keeper but not tensioned; c) the lever arm In a so position where the latch arm Is tensioned and secured.

   9 An over-centre latch in accordance with claim 7 or 8, wherein the detents are sufficient to assist in the latch remaining closed to prevent accidental opening.

   An over-centre latch in accordance with any preceding claim, wherein each component part of the latch is formed from a plastics material by mounding.

   11. An over-centre latch in accordance with any preceding claim, wherein the latch arm has an arch shape with each end terminating In a retroverted portion to engage, respectively, the keeper lip and the latch arm pivotal connection, the arch shape providing a degree of flexure under loading to accommodate the over-centre transitional movement whilst still providing a retention force preventing the lever arm returning to the unlatched position 12 An over-centre latch in accordance with any preceding claim, wherein the second transverse web of the lever arm forming the second pivotal o connection with the base has a planar portion adjacent a lower side of the latch arm, initial rotation of the lever arm about the axis of the second pivotal connection initially producing contact between an edge of the planar portion and the lower side of the latch arm and imparting a lifting force to the latch arm.

   13. An over-centre latch in accordance with any preceding claim, wherein, and in a closed position, the latch arm partially locates, at the other end, within the spaced side members of the lever arm.

   14 An over-centre latch in accordance with any preceding claim 13, wherein the other end of the latch arm has a reduced width, the one end of the latch arm having a width defined by side surfaces coextensive with the side surfaces of the spaced side members of the lever arm.

   An over-centre latch constructed and arranged to function as described herein and as Illustrated with reference to the drawings.